v2.1.0: configurable base controller + chart timezone

[vishaltps]

Summary

• New SolidQueueMonitor.base_controller_class config lets host apps plug the dashboard into their existing auth chain (Devise, Pundit, OmniAuth, custom sessions) instead of being stuck on HTTP Basic.
• Engine helpers (render_chart, etc.) wired explicitly via helper Engine.helpers so they keep working when the parent is not ActionController::Base.
• Chart timezone behaviour (already correct via Time.current since v2.0) now pinned by specs running in America/Los_Angeles.

Problem

Single biggest adoption blocker reported after v2.0.0: the engine's ApplicationController hardcoded ActionController::Base, so teams with Devise/Pundit/etc. had no clean integration point. Their workaround was monkey-patching SolidQueueMonitor::ApplicationController via to_prepare — fragile and breaks on gem upgrade.

Solution

• lib/solid_queue_monitor.rb: top-level base_controller_class accessor (default "ActionController::Base"). Top-level rather than inside setup do |config| because it's a class-loading concern, not a runtime preference — same pattern as Mission Control: Jobs.
• app/controllers/solid_queue_monitor/application_controller.rb: inherits via SolidQueueMonitor.base_controller_class.safe_constantize || ActionController::Base. safe_constantize keeps boot resilient against typos / dev-mode autoload edge cases.
• Same controller now does helper SolidQueueMonitor::Engine.helpers so view methods like render_chart keep resolving regardless of parent class.

Changes

• lib/solid_queue_monitor.rb — add base_controller_class accessor + DEFAULT_BASE_CONTROLLER_CLASS constant.
• app/controllers/solid_queue_monitor/application_controller.rb — dynamic parent + explicit engine-helper inclusion.
• spec/lib/solid_queue_monitor_spec.rb (new) — accessor coverage, parent-class resolution, and a regression guard that asserts engine helpers stay wired.
• spec/services/solid_queue_monitor/chart_data_service_spec.rb — new context running in America/Los_Angeles with a frozen UTC time, asserting labels render in PT not UTC.
• README.md — new "Custom Authentication" subsection (minimal + role-gated examples), commented base_controller_class line in the main config block.
• CHANGELOG.md — [2.1.0] - 2026-05-13 entry.
• lib/solid_queue_monitor/version.rb — 2.0.0 → 2.1.0.

Testing

• bundle exec rspec — 326 examples, 0 failures (was 315 in v2.0.0; +11 new).
• bundle exec rubocop — 73 files, no offenses.
• Manual test in solid_queue_test host app:
  • default behaviour (HTTP Basic) unchanged
  • custom AdminController with before_action correctly gates the dashboard
  • engine helpers (render_chart, etc.) resolve under the custom parent

Checklist

• Default behaviour byte-identical to v2.0.0 — both features opt-in / non-breaking
• CSP compatibility preserved (no new inline handlers or style= attrs)
• CHANGELOG entry under [2.1.0]
• Version bumped
• Self-review completed